This invention relates to tone-arm elements, and more particularly, to those elements constituting the non-vibration system of a tone-arm for a record player, such as tone-arm pipes, cartridge bodies, head shells, arm bases and the like.
To enhance the trackability of a cartridge, it is desirable to reduce the mass of a cartridge-supporting or non-vibration system while obtaining an increased internal loss to prevent partial vibration. The mass of a tone-arm system may be reduced simply by making an arm pipe, a head shell and other tone-arm elements lighter. However, if wall thickness is reduced for this purpose, a correspondingly reduced stiffness tends to cause unwanted partial vibration, debasing the sound quality reproduced through such a tone-arm system. There is a need for arm pipes, head shells and cartridge bodies formed from a light-weight material which has a high stiffness or high modulus of elasticity as well as a sufficient internal loss.
Those arm pipes and head shells formed from a conventional metallic material such as aluminum, titanium, beryllium, etc. are not satisfactory due to poor internal loss (damping) though they have a high modulus of elasticity. Also known are arm pipes and head shells formed from fibrous carbon materials which are physically excellent as they have a high specific modulus of elasticity and a relatively large internal loss. However, carbon fibers must be compounded with a synthetic resin before arm pipes or head sheels can be molded therefrom. Such composite carbon fiber-resin materials show a reduced specific modulus of elasticity.
Recently, the inventors proposed arm pipes and head shells molded from a kneaded mixture of polyvinyl chloride and flaky graphite powder and having advantages of light weight, high elasticity and high internal loss as disclosed in U.S. Ser. No. 147,866 (filed May 8, 1980). The proposed tone-arm elements have improved properties which are not found in prior art materials or elements. In various applications of the previously proposed material, the inventors encountered a problem that these elements are still insufficient in heat resistance. These elements tend to be deformed particularly when exposed to the sun in summer or used in the tropics.